"I am leaving the post of prime minister this evening with a feeling of accomplishment," Laurent Lamothe said in a televised address.
Protesters had called for President Michel Martelly and Mr Lamothe to resign.
Mr Martelly was to have called polls in 2011, but they were postponed in a stalemate over electoral law.
Opposition politicians accuse President Martelly of wanting to rule by decree and that legislation that would authorise the vote unfairly favours the government.
The government argues that opposition politicians are dragging their feet in the hope of extending their time in office without elections.
Parliament's mandate expires in January, and unless elections are held, Mr Martelly would rule by decree.
A commission set up to break the stalemate said on Friday that Mr Lamothe should resign, along with the head of the Supreme Court and the country's election commission.
Mr Martelly said earlier that the accepted the commission's findings, and would meet government officials on Monday to discuss them.
Haiti is also still struggling to recover from a devastating 2010 earthquake.
